The long term goal of this program of research is to understand biopsychosocial processes associated with children's illness behavior (i.e., somatic complaints, disability, health service utilization). We are particularly concerned with children who maintain extensive illness behavior that is out of proportion to medical findings. Children with recurrent abdominal pain (RAP) serve as a prototype for our study of children with high levels of illness behavior not associated with significant organic disease. Our recent work showed that the within-subject correlation between daily stressors and somatic complaints was significantly stronger for children with RAP than for Well children, suggesting that children with RAP may be distinguished from their peers by a tendency to react to stress with somatic symptoms. In the next stage of this research, our first major goal is to identify mechanisms linking environmental and somatic stressors to illness behavior. Specifically, using experimental methods in a laboratory setting, we will: (Aim 1) assess the influence of a challenging cognitive task on children's physiological activity, selective attention to somatic cues, and symptom reporting; and (Aim 2) assess the influence of visceral stimulation and parental responses on children's pain complaints. In addition, we will create an index of stress reactivity based on laboratory performance and will assess the utility of that index in predicting health outcomes. Our second major goal is to identify subgroups of RAP that may have different treatment needs. Specifically, we will: (Aim 3) identify diagnostic subgroups of patients with RAP and compare these with respect to symptomatology, psychosocial characteristics, and course of illness over 3 months, and (Aim 4) cross-validate a typology of pain coping profiles for patients with RAP and assess the utility of these profiles in predicting health outcomes. The proposed project combines self-report and psychophysiological measures, experimental laboratory methods, and a longitudinal design. Participants in the Baseline Assessment will include 396 patients with RAP and 842 Well children (ages 8-15). From these groups, children and their parents will be recruited for the Laboratory Computer Task (n =200) and the Laboratory Water Load Task (n = 220). Study results have the potential to yield insights into mechanisms linking stress to illness behavior in RAP and, in addition, to identify intervention targets that prepare children and their parents to better manage RAP.